The ultimate goal of this Program Project is to develop novel therapeutic approaches for advanced childhood sarcoma. While over 70% of children with sarcoma are considered cured, the outcome is still poor for those with advanced or metastatic disease. Specifically, the 5-year event free survival rates are 30 percent or less in children with advanced or metastatic Ewing sarcoma, osteosarcoma or rhabdomyosarcoma and intensive chemo-radiotherapy has not significantly altered this outcome. As additional cytotoxic drugs alone are unlikely to increase cure rates, alternative and complimentary approaches should be explored. This Program centers around three separate but integrated signaling pathways shown to be active in childhood sarcomas. The projects will characterize the interrelationship of these pathways and identify combinatorial inhibitory approaches most likely to yield biologic activity in the clinical setting. Project 1 will define the role of the classicalNF-?B pathway in regulating metabolism of sarcomas through a shift to the glycolytic pathway. Our, and other, data indicate that NF-?B signaling impacts STAT3 signaling and that components of the NF-?B pathways interact with mTOR to modulate cellular metabolism. Project 2 focuses on how STAT3 signaling regulates the proliferation and survival of sarcoma cells, and on the development LY5, a highly selective allosteric inhibitor of STAT3. We show that both NF-?B and IGF signaling pathways regulate STAT3 in sarcoma cells. Project 3 will examine intrinsic and acquired resistance to IGF-targeted therapies with respect to proliferation, survival and angiogenesis. Our data demonstrate that IGF-1 protects against apoptosis induced by mTORC1 inhibition and will explore the role of STAT3 and NF-?B in protection from apoptosis. The Program is supported by three shared resources. Core A (Administration and Biostatistics) coordinates communication, program interactions, and provides a centralized mechanism for biostatistical support. Core B (Xenograft and Cell Line) provides unique mouse models of childhood sarcoma and expertise. And Core C (Comparative Animal Core) supplies expertise in histopatholgy, fresh canine tumor specimens, and access to dogs with spontaneous osteosarcoma for preclinical testing of novel therapeutics.